In the closing days of World War II, the United States was facing a difficult decision. In the face of increasingly fanatical Japanese resistance during the island-hopping Pacific campaign, American casualties were increased dramatically. 

Fearing that an invasion of Japan would cost hundreds of thousands of U.S. casualties and millions of Japanese, the decision by President Truman to drop the atomic bomb on Japan was not made lightly. The atomic bomb was dropped at Hiroshima and Nagasaki. According to some estimates, more than 226,000 people, mostly civilians, died in the two blasts. Following the bombings, Japan surrendered. It was the only time that nuclear weapons have been used in war. 

By August of 1945, there was little doubt that an invasion of mainland Japan was going to happen. The Japanese had been pushed all the way across the Pacific, had their war industries smashed, and were starving. But they weren’t yet defeated. Although they still controlled parts of New Guinea, the Dutch East Indies, and Indochina, their forces there were cut off and had no hope of coming to the assistance of the Japanese islands. 

The “Little Boy” atomic bomb.

The Japanese still had massive numbers of troops in China but defeats in the Philippines, the Marshall Islands, Iwo Jima, and Okinawa had the U.S. on their doorstep. B-29 bombers could now hit Japanese cities and were close enough to have fighter cover all the way to Japan and back. But those American victories were very costly. Where Japanese casualties had been five to six times that of American troops earlier in the war, by the time Okinawa was finally secured in June 1945, the ratios had dropped to 2-1. Japanese troops would rather fight to the death than surrender. Since the battle of the Philippine Sea, Japanese suicide pilots (kamikaze), had also been taking a toll on American warships and lives.